Fructose diphosphate aldolase-class I (Schiff base) fromMycobacterium tuberculosis H37Rv

An aldolase was partially purified from fermenter grownMycobacterium tuberculosis H₃₇Rv cells. The aldolase has a molecular weight of 150,000, possesses a tetrameric structure and cleaves both fructose diphosphate and fructose-1-phosphate, the former being cleaved 17 times faster. The enzyme was inactivated by treatment with NaBH₄ in the presence of fructose diphosphate or dihydroxyacetone, phosphate suggesting Schiff base formation during its catalytic function. Thiol reagents, EDTA and metal ions had no apparent effect on the aldolase activity. These results show that aldolase is of Class I type. However, this enzyme, unlike the mammalian Class I aldolase, was unaffected by carboxypeptidase A. N-ethylmaleiniide and dithionitrobenzoic acid.     

The origin and behavior of two isodicentric bisatellited chromosomes.

Karyotyping revealed three cell lines in a boy with mental retardation and few other abnormalities. Thirty cells exhibited a normal karyotype, and 54 had an extra acrocentric chromosome of E group size with satellites on the long and short arms. The remaining 20 cells each had, in addition to the first marker (M1), a second tiny bisatellited chromosome (M2). C-banding demonstrated that both markers were dicentric. G-, C-, and Q-banding and satellite association data were consistent with the markers having originated from chromosome 15 material. We propose that M1 was formed from a meiotic breakage and a chromatid fusion in the proximal long arms of an acrocentric pair. This would have produced a symmetrical isodicentric chromosomes, plus one or two acentric fragments. M2 then could have resulted from a dicentric bridge-break-synthesis-reunion phenomenon. This model of abnormal meiotic exchange can be generalized to encompass the formation of other dicentric isochromosome cases of isochromosome X.     

Cytological study of pollen tube growth and early seed development inPetunia inflata

Pollen tube growth from the stigma into the ovule, and the early fruit and seed development following fertilization were examined using fluorescence microscopy, scanning electron microscopy and light microscopy inPetunia inflata. After growing intercellularly in the transmitting tract for 24–36 hr, the pollen tubes emerged into the top part of the ovary cavity and grew along the surface of the septum to reach the ovule. It grew around the furnicle and penetrated the micropyle to enter the embryo sac for fertilization. After fertilization, the endosperm nucleus divided first before the embryo, and the cell wall formation occurred following the division, exhibiting the pattern of cellular type of endosperm development. The first division of the zygote did not occur until 3 days after pollination. At 6 days after pollination, the seeds grew considerably and the endosperm has gone through multiple rounds of cell division. High starch formation in the integument, especially around the embryo sac, was also observed.     

RAPD analysis of natural populations of Acanthopanax brachypus

Random amplified Polymorphic DNA(RAPD) analysis is a new technology of molecular marking which has proved very powerful in detecting genetic diversity at the level of population.The genomic DNAs used in our experiment were extracted from fresh leaves taken from 59 individuals sampled from three natural populations in Yan an,Shanxi Province.Through more than 2,000 PCRs,deep-going RAPD analysis was carried out on DNA samples from 49 inviduals.The percentage of polymorphic RAPD loci found in these three populations were respectively 27.2%,18.6% and 5.4%;the average genetic distances within population,0.055,0.026 and 0.008;the average genetic distances between populations (I-II),(I-III) and (II-III),0.105,0.096 and 0.060.The genetic diversity of A.brachypus within and between populations was found,for the first time,to be rather poor,thus revealing innate factors as the cause contributing to its endangered status.In addition,our work also provides basic materials for elucidating the underlying cause of its endangerment and for its protection biology.     

Characterization of a mutant calcineurin A alpha gene expressed by EL4 lymphoma cells.

The calmodulin-stimulated phosphatase calcineurin plays a critical role in calcium-dependent T-lymphocyte activation pathways. Here, we report the identification of a missense mutation in the calcineurin A alpha gene expressed by EL4 T-lymphoma cells. This mutation changes an evolutionarily conserved aspartic acid to asparagine within the autoinhibitory domain of the calcineurin A alpha protein. A comparison of wild-type and mutant autoinhibitory peptides indicates that this amino acid substitution greatly reduces inhibition of calcineurin phosphatase activity. Additional peptide inhibition studies support a pseudosubstrate model of autoinhibitory function, in which the conserved aspartic acid residue may serve as a molecular mimic of either phosphoserine or phosphothreonine. Expression of the mutant calcineurin appears to affect cellular signal transduction pathways, as EL4 cells can be activated by suboptimal concentrations of calcium ionophore in the presence of phorbol esters. Moreover, this phenotype can be transferred to Jurkat T cells by transfection of the mutated calcineurin gene. These findings implicate a conserved aspartic acid in the mechanism of calcineurin autoinhibition and suggest that mutation of this residue is associated with aberrant calcium-dependent signaling in vivo.     

不同地点杨树无性系树高和胸径变异分析及生长模型构建

以不同地点30个白杨杂种无性系为材料,对其不同树龄的树高和胸径进行调查,对获得数据进行变异分析并构建生长曲线模型,方差分析结果表明地点间、无性系间、地点与无性系交互作用间均达到极显著差异水平(P0.01);树高和胸径表型变异系数变化范围分别为15.34%~23.80%和19.42%~31.88%;所有性状重复力较高,变化范围为0.797 7~0.985 9;模型构建结果表明,根据杨树无性系苗期树高和胸径构建的指数函数模型拟合度r2分别达0.82和0.87,拟合效果较好。利用模型对未测定数据进行估算,无论树高还是胸径,冠县无性系的最初生长量最高,而峰峰的树高和威县的胸径生长速率最快。基因型与环境具有明显的交互作用,不同无性系在相同地点表现差异较大,相同无性系在不同地点也呈现明显差异,表明无性系评价选择需要考虑环境因素,适地适树的进行选择。构建的模型可以为林木生长量预测提供理论依据。     

Propensity Score-Based Approaches to Confounding by Indication in Individual Patient Data Meta-Analysis: Non-Standardized Treatment for Multidrug Resistant Tuberculosis

Background

In the absence of randomized clinical trials, meta-analysis of individual patient data (IPD) from observational studies may provide the most accurate effect estimates for an intervention. However, confounding by indication remains an important concern that can be addressed by incorporating individual patient covariates in different ways. We compared different analytic approaches to account for confounding in IPD from patients treated for multi-drug resistant tuberculosis (MDR-TB).

Methods

Two antibiotic classes were evaluated, fluoroquinolones—considered the cornerstone of effective MDR-TB treatment—and macrolides, which are known to be safe, yet are ineffective in vitro. The primary outcome was treatment success against treatment failure, relapse or death. Effect estimates were obtained using multivariable and propensity-score based approaches.

Results

Fluoroquinolone antibiotics were used in 28 included studies, within which 6,612 patients received a fluoroquinolone and 723 patients did not. Macrolides were used in 15 included studies, within which 459 patients received this class of antibiotics and 3,670 did not. Both standard multivariable regression and propensity score-based methods resulted in similar effect estimates for early and late generation fluoroquinolones, while macrolide antibiotics use was associated with reduced treatment success.

Conclusions

In this individual patient data meta-analysis, standard multivariable and propensity-score based methods of adjusting for individual patient covariates for observational studies yielded produced similar effect estimates. Even when adjustment is made for potential confounding, interpretation of adjusted estimates must still consider the potential for residual bias.     

Enhanced biocatalytic activity of immobilized <Emphasis Type="Italic">Pseudomonas cepacia</Emphasis> lipase under sonicated condition

The present work reports the use of biocatalyst and ultrasound for greener synthesis of cinnamyl propionate. The lipase Pseudomonas cepacia was immobilized on a copolymer of hydroxypropyl methyl cellulose and polyvinyl alcohol. This biocatalyst was used for ultrasound-assisted synthesis of cinnamyl propionate with the detailed optimization of various reaction parameters. Besides this, protocol was extended to synthesize various industrially important propionate esters. In addition to this, different enzyme-kinetic parameters such as r _max and K _{m(vinyl propionate),} K _{m(cinnamyl alcohol)} and K _{i(cinnamyl alcohol)} were studied which presented ordered bi–bi mechanism with an inhibition by cinnamyl alcohol. The developed biocatalyst demonstrated enhancement in catalytic activity and recyclability up to five recycles. Moreover, the biocatalyst was tested to investigate the effects of sonication via various characterization techniques such as scanning electron microscopy, thermogravimetry, and water content analysis.     

EspP,an Extracellular Serine Protease from Enterohemorrhagic E. coli,Reduces Coagulation Factor Activities,Reduces Clot Strength,and Promotes Clot Lysis

Background

EspP (E. coli secreted serine protease, large plasmid encoded) is an extracellular serine protease produced by enterohemorrhagic E. coli (EHEC) O157:H7, a causative agent of diarrhea-associated Hemolytic Uremic Syndrome (D+HUS). The mechanism by which EHEC induces D+HUS has not been fully elucidated.

Objectives

We investigated the effects of EspP on clot formation and lysis in human blood.

Methods

Human whole blood and plasma were incubated with EspP^WT at various concentrations and sampled at various time points. Thrombin time (TT), prothrombin time (PT), and activated partial thromboplastin time (aPTT), coagulation factor activities, and thrombelastgraphy (TEG) were measured.

Results and Conclusions

Human whole blood or plasma incubated with EspP^WT was found to have prolonged PT, aPTT, and TT. Furthermore, human whole blood or plasma incubated with EspP^WT had reduced activities of coagulation factors V, VII, VIII, and XII, as well as prothrombin. EspP did not alter the activities of coagulation factors IX, X, or XI. When analyzed by whole blood TEG, EspP decreased the maximum amplitude of the clot, and increased the clot lysis. Our results indicate that EspP alters hemostasis in vitro by decreasing the activities of coagulation factors V, VII, VIII, and XII, and of prothrombin, by reducing the clot strength and accelerating fibrinolysis, and provide further evidence of a functional role for this protease in the virulence of EHEC and the development of D+HUS.